.#{$selectize}-dropdown.plugin-optgroup_columns {
  .#{$selectize}-dropdown-content {
    display: flex;
  }

  .optgroup {
    border-right: 1px solid #f2f2f2;
    border-top: 0 none;
    flex-grow: 1;
    flex-basis: 0;
    min-width: 0;
  }
  .optgroup:last-child {
    border-right: 0 none;
  }
  .optgroup:before {
    display: none;
  }
  .optgroup-header {
    border-top: 0 none;
  }
}